Question

Explain the reason for the following: 
(i) On putting a zinc rod in copper sulphate solution, its blue colour vanishes slowly.
(ii) Ionic compounds have high melting points.

Hint:

The stronger the electrostatic attraction between ions, the higher the melting and boiling points of ionic compounds.

Answer 1

(i) On putting a zinc rod in copper sulphate solution, its blue colour vanishes slowly.
The blue color of copper sulphate is due to the presence of copper ions (\( \text{Cu}^{2+} \)). When zinc is placed in copper sulphate solution, zinc displaces copper from the solution, forming zinc sulphate and leaving behind the colorless zinc ions. This is a redox displacement reaction.
\[ \text{Zn} + \text{CuSO}_4 \to \text{ZnSO}_4 + \text{Cu} \] (ii) Ionic compounds have high melting points.
Ionic compounds have high melting points due to the strong electrostatic forces between positively and negatively charged ions. These forces require a significant amount of energy to break, resulting in high melting points for ionic solids.